It is the broad objective of this project to study some of the bacterial products present in human plaque, specifically the activation and role of certain endogenous compounds which act as inflammatory mediators. The major objective of this study is the determination of the sequence of inflammatory mediators released during acute gingival inflammation induced by bacterial endotoxins, plaque extracts, and other bacterial products with special emphasis on the determination of the kinds and levels of inflammatory mediators, of the time course of their appearance, and of the inflammatory events related to their presence. Emphasis is placed on measurement of kallikrein and kinin activity and alterations in histamine levels in relation to their probable role in mediating certain aspects of the acute gingival inflammatory reaction such as increased vascular permeability. The effects of various inhibitors of endogenous inflammatory mediator systems on the acute gingival inflammatory reaction to bacterial products is being studied. The delineation of at least some of the mechanisms involved in gingival inflammation comprises a basis for the formulation of more effective preventive or therapeutic measures.